Both government and industry have conducted extensive research into developing fabrics for the seat cushions of airplanes that would either be non-flammable or at least retard the propagation of a fire. In conjunction with finding an effective material to act as a fire barrier, consumer considerations require that any such materials be functional, aesthetically acceptable and reasonably priced. Suitable barriers do exist such as needle punched aramids, however, these barriers are difficult to cut and sew, heavy and often provide less than desired comfort.
Unfortunately, past efforts to develop a suitable fire barrier have not been very effective. Thus, even fabrics that will not ignite from a smoldering cigarette and that are considered to be class 1 fabrics under the UFAC upholstery fabric classification test will burn when placed in contact with an open flame. Consequently, this leads to the ignition of an underlying foam cushion.
Inherently, flame-retardant fibers are well-known to those skilled in the art. These fibers, known as matrix fibers, though useful because of their flame-retardant qualities, are not strong enough to form their own fabrics, tend to have a non-uniform composition, are not succeptible of being easily dyed, and, in general, are not alone suitable for production into fabrics to form coverings for seat cushions. On the other hand, conventional natural and synthetic fibers (staple fibers) which are alone suitable for production into seat cushions are not inherently flame-retardant.
Many types of flame resistant fabrics, i.e., fabrics which are self-extinguishing when the ignition source is removed, have been provided by the prior art. For example, fabrics of normally flammable fibers, e.g., cotton, rayon, etc. have been treated with innumerable flame resistant surface coating compositions. More recently, flame resistant fabrics have been prepared from either normally flammable synthetic fibers, e.g., rayon, polyolefins, polyesters, acrylics, etc., which have been spun with flame retardant additives or from other synthetic fibers which are spun from polymers which are inherently flame resistant, PG,4 e.g., polyvinylchloride, polytetrafluoroethylene, polymetaphenyleneisophthalamide. Although such flame resistant fabrics have found substantial application in carpets, draperies, upholstery, etc. and also in garments such as costumes, sleepwear, etc. where flame propagation from inadvertently applied ignition sources is to be avoided, in general, such fabrics are not satisfactory for upholstery or seat cushion covering, especially for airplanes, since they exhibit shrinkage or rapid break open on exposure to intense heat fluxes. The art has provided a limited number of super-high-temperature organic polymeric fibers, e.g., polybenzimidazoles, polyoxadiazoles, polyparaphenylene terephthalamide and certain heat-treated/cyclized acrylic, which in fabric form can survive intense thermal fluxes, at least for a worthwhile interval. However, such fabrics also exhibit one or more negatives, such as limited durability (poor abrasion resistance, low flex life) and poor dyeability. In some instances the polymer used for the fiber of the fabric is inherently highly colored.
It is not sufficient that the fabric merely be flame resistent and possess abrasion resistance. To be completely acceptable, the fabric must also be lightweight, conformable, nonscratchy, durable in normal use, dyeable, etc. in order that the seat covering made therefrom will be sufficiently comfortable and aesthetically attractive.
European Patent Application 0199567 of McCullough, et al discloses non-linear carbonaceous fibers which are used in the structures and fabrics of the present invention.
The carbonaceous fibers of the invention according to the test method of ASTM D 2863-77 have a LOI value greater than 40.
The term "Reversible Deflection" as used herein applies to a helical or sinusoidal compression spring. Particular reference is made to the publication "Mechanical Design--Theory and Practice", MacMillan Publ. Co., 1975, pp 719 to 748; particularly Section 14-2, pages 721-24.